Raman laser cooling of solids

• Published in: Journal of luminescence 2013-01, Vol.133 (1), p.10-14
• Main Author: Rand, Stephen C.
• Format: Article
• Language: English
• Subjects: Broadband; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cooling; Electronics; Exact sciences and technology; Fluorescence; Fundamental areas of phenomenology (including applications); Narrowband; Nonlinear optics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical refrigeration; Optics; Other solid inorganic materials; Photoluminescence; Photons; Physics; Rare earth metals; Stimulated raman scattering; cars; Three dimensional
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2012.01.019

A new approach is proposed for 3-D laser cooling of solids. Stimulated Raman scattering on a narrowband electronic transition is used in conjunction with 1-photon optical pumping on a broadband transition to provide a mechanism that cools all the vibrational modes of solids while conserving energy and momentum, photon by photon. The individual steps in the 2-photon Raman process are 4f–5d and 5d–4f transitions which are electric-dipole-allowed (broadband) transitions that form a Λ-system. By contrast, the 2-photon transition between the 4f states of the rare earth ion is narrowband. By considering examples of Ce3+ ions in Y3Al5O12 and CeF3, elevated transition rates are predicted to offer substantial improvement over anti-Stokes fluorescence cooling when all 1-photon detunings exceed their corresponding Stokes shifts. ► A method of optical refrigeration of solids to sub-Kelvin temperatures is outlined. ► Stimulated Raman transitions plus fast fluorescence can cool solids effectively. ► A new, red detuning condition that avoids configuration relaxation is identified.